Synthetic surface coverings are well known. Generally they are made of rubber, polyolefins, polyesters, polyamides or PVC. They present specific mechanical properties, particularly in terms of mechanical resistance, wear and indentation resistance, but also in terms of comfort, softness, sound and heat insulation.
In the context of the present document, laminate floor coverings with a fibreboard core are not considered synthetic floor coverings.
Among polymer-based surface coverings, two main categories can be identified. Homogenous surface coverings are coverings comprising agglomerated particles, generally obtained by cutting or shredding a sheet made from a composition which comprises a polymer-based material, and wherein no bottom layer, or backing, conferring structural stability to the surface covering, is used. Heterogeneous or multilayer surface coverings are coverings comprising one or more lower layers and one or more transparent upper layers (wear layer and, possibly, a hard top varnish). These coverings may comprise a decorative pattern imitating the aesthetic appearance of natural floorings such as wood or stone floorings. Such decorative pattern may be printed on the bottom face of the wear layer, on the top face of a core or support layer or on an additional layer (print layer) that is inserted between the core or support layer and the wear layer.
Floor covering elements (hereinafter: floor panels) with conjugate connection profiles are known in the art. One of their simplest embodiments comprises a tongue profile (or male profile) and a groove profile (or female profile). Each floor panel has one or two edges (lateral faces) with a tongue profile and the opposite one or two edges are provided with respectively complementary groove profiles. While such profiles have first been used on wood floor panels, they have meanwhile also been applied to laminate floor panels. For instance, WO 97/47834 discloses a floor covering, consisting of hard floor panels (i.e. laminate panels with a fibreboard base or wood panels) which, at least at the edges of two opposite sides, are provided with coupling parts, cooperating with each other, substantially in the form of a tongue and a groove. The coupling parts, which are integrated into the floor panels, mechanically interlocking in order to prevent two coupled floor panels from drifting apart into a direction perpendicular to the adjacent edges and parallel to the underside of the coupled floor panels. In the engaged state of two floor panels, the coupling parts are slightly elastically deformed in such a way that they exert on each other a tension force that urges the floor panels toward each other.